Thermosetting coating composition of acrylic interpolymers

Abstract

Thermosetting powder coating compositions comprising (A) a carboxyl functional thermosetting acrylic interpolymer prepared by the polymerization of a monomeric mixture comprised of (1) a vinyl aromatic hydrocarbon, (2) a methacrylic acid ester, (3) an acrylic acid ester and (4) an olefinically unsaturated carboxylic acid and (B) at least one curing agent selected from the group consisting of di- and multifunctional epoxides.

What is claimed is: 
     
       1. Thermosetting powder coating compositions consisting of (A) at least one carboxyl functional thermosetting acrylic interpolymer having a second order transition temperature ranging from 30° to 80° C. and prepared by the polymerization in the presence of a chain transfer agent at a temperature in the range of from about -10° C. to about 100° C. of a monomeric mixture consisting of (1) from 0 to 50 percent by weight of a vinyl aromatic hydrocarbon, (2) from 20 to 88 percent by weight of a methacrylic acid ester, (3) from 10 to 40 percent by weight of an acrylic acid ester and (4) from 2 to 20 percent by weight of an olefinically unsaturated carboxylic acid containing from 1 to 3 carboxyl groups selected from the group consisting of acrylic acid, methacrylic acid, fumaric acid, maleic acid, methyl maleic acid, methyl fumaric acid, ethyl maleic acid and itaconic acid propene-1,2,3-tricarboxylic acid, all percentages based on the total weight of monomers charged and (B) at least one curing agent selected from the group consisting of di- and multifunctional epoxides derived from the reaction of epichlorohydrin or glycidyl ether with a polyhydric phenol or a polyhydric compound selected from the group consisting of glycerol, polyglycols, novalac resins and polynuclear polyhydroxy phenols and polyepoxides of olefins, cycloolefins and cyclic dienes, and wherein component (A) ranges from 50 to 92 percent by weight and component (B) ranges from 50 to 8 percent by weight all based on total combined weight of components (A) and (B). 
     
     
       2. Thermosetting powder coating compositions according to claim 1 wherein the carboxyl functional thermosetting acrylic interpolymer has a second order transition temperature ranging from 30° to 80° C. and is prepared by emulsion polymerization of a monomeric mixture of (1) from 0 to 40 percent by weight of a vinyl aromatic hydrocarbon, (2) from 30 to 60 percent by weight of a methacrylic acid ester, (3) from 15 to 40 percent of an acrylic acid ester and (4) from 6 to 12 percent by weight of an olefinically unsaturated carboxylic acid containing from 1 to 3 carboxyl groups, all percentages based on the total weight of monomers charged and wherein the curing agent is selected from the group consisting of di- and multifunctional epoxides. 
     
     
       3. Thermosetting powder coating compositions according to claim 1 wherein the monomeric mixture employed to prepare the carboxyl functional thermosetting acrylic interpolymer, component (A) is (1) styrene, (2) methyl methacrylate, (3) butyl acrylate and (4) methacrylic acid. 
     
     
       4. Thermosetting powder coating compositions according to claim 1 wherein the carboxyl functional thermosetting acrylic interpolymer has a second order transition temperature ranging from 45° to 70° C. and is prepared by emulsion polymerization of a monomeric mixture of (1) from 18 to 37 percent by weight of a vinyl aromatic hydrocarbon, (2) from 30 to 56 percent by weight of a methacrylic acid ester, (3) from 20 to 40 percent by weight of an acrylic acid ester and (4) from 6 to 12 percent by weight of an olefinically unsaturated carboxylic acid containing from 1 to 3 carboxyl groups and wherein the curing agent is prepared by the reaction of epichlorohydrin or an equivalent 1,2-epoxy compound thereof with at least one compound selected from the group consisting of polyhydric phenols, glycerol, polyglycols, novalac resins and polynuclear polyhydroxy phenols. 
     
     
       5. Thermosetting powder coating compositions according to claim 4 wherein the epoxide has an average molecular weight ranging from 700 to 2000, an epoxide equivalent weight ranging from 450 to 1000 and a Durran's softening point ranging from 65° to 105° C. 
     
     
       6. Coatings of good surface uniformity, smoothness, gloss, hardness, adhesion, toughness, chemical resistance and good edge coverage consisting of (A) a carboxyl functional thermosetting acrylic interpolymer derived from the emulsion polymerization of a monomeric mixture consisting of (1) from 18 to 37 percent by weight of a vinyl aromatic hydrocarbon,   (2) from 30 to 56 percent by weight of a methacrylic acid ester,   (3) from 20 to 40 percent by weight of an acrylic acid ester and   (4) from 6 to 12 percent by weight of an olefinically unsaturated carboxylic acid and containing from 1 to 3 carboxyl groups, wherein all percentages are based on the total weight of monomers charged and wherein said interpolymer has a second order transition temperature ranging from 45° to 70° C., and     (B) at least one curing agent selected from the group consisting of di- and multi-functional epoxides derived from the reaction of epichlorohydrin or glycidyl ether with a polyhydric phenol or a polyhydric compound selected from the group consisting of glycerol, polyglycols, novalac resins and polynuclear polyhydroxy phenols and polyepoxides of olefins, cycloolefins and cyclic dienes, and   (C) a pigment, wherein (A) ranges from 50 to 92 percent by weight and (B) ranges from 50 to 8 percent by weight of the total combined weight of (A) and (B).     
     
     
       7. The coatings of claim 6 wherein the carboxyl functional thermosetting acrylic interpolymer, (A), is derived from the emulsion polymerization of a monomeric mixture of (1) styrene, (2) methyl methacrylate, (3) butyl acrylate and (4) methacrylic acid. 
     
     
       8. The coatings of claim 6 wherein the curing agent, (B), is selected from the group consisting of di- and multifunctional epoxides prepared by the reaction of epichlorohydrin with at least one compound selected from the group consisting of polyhydric phenols, glycerol, polyglycols, novalac resins and polynuclear polyhydroxy phenols. 
     
     
       9. The coatings of claim 8 wherein the curing agent, (B), is selected from the group consisting of di- and multifunctional epoxides prepared by the reaction of epichlorohydrin with a polyhydric phenol. 
     
     
       10. The coatings of claim 9 wherein the curing agent, (B), is selected from the group consisting of di- and multifunctional epoxides prepared by the reaction of epichlorohydrin and the polyhydric phenol, 2,2-bis(p-hydroxyphenyl) propane. 
     
     
       11. The coatings of claim 8 wherein the curing agent, (B), has an average molecular weight ranging from 700 to 2000, an epoxide equivalent weight ranging from 450 to 1000 and a Durran's softening point ranging from 65° C. to 105° C.